Easy Step-by-Step guide to resolving slow Wi-Fi and Internet with intel dual band wireless-ac 3165 and 31** variants on Windows 10

So this started at the beginning of last week with a report from a member of teaching staff experiencing really low Internet speeds while browsing via Wi-Fi with an Intel Dual Band Wireless AC-3165. Connected via LAN gave consistent download speeds of > 80Mbps but switch to Wi-Fi and they got barely 0.02Mbps.

After many hours trawling through Event Viewer and changing, testing and changing back advanced Wi-Fi settings I came across “Receive Segment Coalescing” see https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2012-r2-and-2012/hh997024(v=ws.11).

Disabling this setting on the network card resolved the issue first time, however it didn’t explain why the laptop had been working for 5 months previously without issue.

After another 3 hours of investigation I found that a recent installation of SonicWALL Global VPN Client must be causing the issue as having remove this and re-enabled Receive Segment Coalescing the issue was no where to be seen.

Steps to disable Receive Segment Coalescing manually on the Intel Dual Band Wireless-AC 3165 :

1) Open an Admin Command Prompt window:
Start > All Apps > Windows System -> Right-click “Command Prompt” > More > Run as administrator

2) Get your network adapter name:
powershell Get-NetAdapter

3) Note your adapter’s name, mine was called “Wi-Fi”

4) Get your network adapter “Receive segment coalescing” (Rsc) settings:
powershell Get-NetAdapterRsc

5) Disable Rsc for your network adapter:
powershell Disable-NetAdapterRsc -Name Wi-Fi

6) Verify Rsc is disabled for ipv4 and ipv6, on your network adapter:
powershell Get-NetAdapterRsc

7) Re-test your wireless internet connection.

An additional workaround for this is also to set the MTU for the Wi-Fi to 1400 instead of the default 1500

Change MTU to 1400

To VIEW your MTU:
Right Click Start > Command Prompt (Admin) > Type or right-click-paste the following command:

netsh interface ipv4 show subinterfaces

To CHANGE your MTU to 1400:

netsh interface ipv4 set subinterface “W-Fi” mtu=1400 store=persistent

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